"HarperCollins will follow the digital publication of these titles with The Legend of Sigurd and Gudrún (£18.99), The Silmarillion (£7.99) and Unfinished Tales (£7.99) on 5th May. These e-book releases are timed to coincide with the hardback of the previously unpublished The Legend of Sigurd and Gudrún."

This was from a British source (here) but hopefully the same will apply in the US